The present disclosure relates to the field of radiography and, in particular, relates to computer tomography (xe2x80x9cCTxe2x80x9d) scanners. Even more particularly, the present disclosure relates to a rotary bearing assembly for a CT scanner.
A typical CT scanner includes a gantry comprising an annular frame for rotatably supporting an annular disk about a rotation or scanning axis of the scanner. The disk includes a central opening large enough to receive a patient extending along the scanning axis, and the disk is rotated about the patient during a scanning procedure. An x-ray tube is positioned on the disk diametrically across the central opening from an array of x-ray detectors. As the disk is rotated, the x-ray tube projects a beam of energy, or x-rays, along a scan plane, through the patient, and to the detector array. By rotating the x-ray source about the scanning axis and relative to the patient, x-rays are projected through the patient from many different directions. An image of the scanned portion of the patient can then be constructed from data provided by the detector array using a computer of the scanner.
U.S. Pat. No. 5,448,608 to Swain et al., entitled Tomographic Scanner Having Center of Rotation for All Physics, discloses a light-weight, portable X-ray tomography system. The system has an annular frame supporting therein a concentric apertured drum rotatable about a rotational axis. A plurality of components for performing a tomographic scan are mounted on the drum with respect to both sides of a mean plane of the drum so as to be dynamically balanced for rotation with the drum about the rotational axis, and so that the center of the mass moment of inertia, the center of rotation, the center of thermal expansion of the drum and components mounted thereon, and the center of the scanning plane substantially coincident on that rotational axis.
U.S. Pat. No. 5,982,844 to Tybinkowski et al., entitled Computed Tomography Scanner Drive System and Bearing discloses a gantry disk sheaved about its perimeter such that the gantry is operable as a driven pulley rotatable about an object to be scanned. A motor assembly mounted to a stationary frame includes a similar sheaved drive pulley, and a belt is tensioned between the drive pulley of the motor assembly and the driven pulley of the gantry disk to transfer rotational motion of the motor to drive the gantry rotationally about the object. In a preferred embodiment, the belt comprises a V-belt or poly-V-belt. The gantry bearings comprise a pair of wire bearings located between an outer ring frame and inner rings supporting the gantry disk, proximal to the gantry center of mass. The disclosed drive system and bearing provides a simple and effective technique for driving the gantry about the object, providing sufficiently accurate angular positioning in a reliable and cost effective drive system.
What is desired is a CT scanner gantry including all of the benefits of the Swain et al. and Tybinkowski et al. patents, as well as additional benefits.
The present disclosure, accordingly, provides a gantry having a novel bearing arrangement for use as part of a CT scanner. The gantry includes an annular outer support, an annular drum concentrically positioned within the outer support, and an annular disk extending radially inwardly from an inner circumferential surface of the drum. The disk is adapted to receive and support computed tomography components.
The annular outer support has a radially inwardly facing, continuous circumferencial bearing chamber, and the drum has a continuous circumferential bearing lip radially extending into the bearing chamber of the outer support to define two circumferential bearing runs within the bearing chamber. The gantry also includes roller bearings in the bearing runs allowing the drum to rotate within the outer support, such that the drum, the disk and computed tomography components supported on the disk are rotatable about a rotation axis of the drum.
According to one aspect, the roller bearings comprise spherical ball bearings, and the gantry also includes bearing wires circumferentially extending within the bearings runs and guiding the roller bearings.
According to another aspect, the drum axially extends between first and second ends, and the bearing lip is equally spaced from the ends, and the annular disk is concentrically aligned with the bearing lip of the drum. Whereby, the bearings are aligned with a center of mass of the gantry.
According to an additional aspect, the disk is adapted to receive x-ray tomography components on both sides of the disk, and to allow at least some of the components to extend through the disk, so that components fixedly mounted on the disk will be substantially balanced for rotation with the disk about the rotation axis.
According to a further aspect, a portion of the radially outermost surface of the rotatable drum is sheaved, and the gantry includes a motor having a sheaved drive pulley, and a belt mounted between the sheaved drive pulley and the sheaved portion of the drum.
The foregoing and other features and advantages of the present disclosure will become more readily apparent from the detailed description of the disclosure, as illustrated in the associated drawings.